Childhood and adolescent leukaemia in a North American population.

OBJECTIVE

This was to describe and analyse incidence and survival data on childhood leukaemias.

SAMPLE

Incident leukaemia cases aged 0-19 from the cancer registry holdings of the province of Saskatchewan for the 60-year period 1932-1991 are the subject of this descriptive report.

METHODS

Age-adjusted, age-specific, histologic-type specific, sex-specific, and cohort-specific incidence trends were reviewed. Univariate and multivariate survival analyses explored the effects of time period, age at diagnosis, gender, and histologic type.

RESULTS

Acute lymphocytic leukaemia (ALL) occurred more commonly in males and before the age of five; the 1982-1991 age-adjusted incidence is 3.1/100,000. Increasing incidence has been consistently noted, but has attenuated since 1971. The relative risk of developing ALL in the first 9 years of life, using children born from 1944 to 1948 as baseline, increased with each successive 5-year birth cohort until 1969-1973; since then the risk has been stable. Other histologic types were rare; over 60 years there were only 85 cases that could be grouped as acute non-lymphocytic leukaemias (ANLL); the 1982-1991 age-adjusted ANLL incidence is 0.6/100,000. A dramatic improvement in survival was seen over the last six decades, primarily for ALL. In ALL, children under five have better survival than older children and adolescents; the reverse is true for ANLL.

CONCLUSIONS

ALL and ANLL are distinctive diseases clinically and the epidemiological findings are likewise distinctive. Our current ALL patterns are consonant with a number of other published reports. However, our small numbers of ANLL limit inferences.